Developer console implementation

Update configs/config.cf file with working variables.

Issue #3.
Developer console implementation

Add DeveloperConsole class with a set of predefined variables (too
long, see DeveloperConsole::addDefaultVariables()) and some default
console commands:
 * unbindall                ; resets key bindings
 * echo "<string>"          ; outputs string value to a console, useful for command batches
 * bind "<key>" "<action>"  ; defines a key binding

Issue #3.